U.S. patent application number 14/200883 was filed with the patent office on 2015-01-08 for developing device and image forming apparatus.
This patent application is currently assigned to FUJI XEROX CO., LTD.. The applicant listed for this patent is FUJI XEROX CO., LTD.. Invention is credited to Kiyohito HORII, Yasutomo ISHII, Hiroaki OKUMA, Toshiaki SUZUKI.
Application Number | 20150010323 14/200883 |
Document ID | / |
Family ID | 52132906 |
Filed Date | 2015-01-08 |
United States Patent
Application |
20150010323 |
Kind Code |
A1 |
OKUMA; Hiroaki ; et
al. |
January 8, 2015 |
DEVELOPING DEVICE AND IMAGE FORMING APPARATUS
Abstract
A developing device includes a developer carrier that has a
cylindrical shape and that rotates while holding developer to
supply the developer to an image carrier on which an electrostatic
latent image is formed; a container that contains the developer
carrier; a discharge-path forming member that forms a discharge
path along which air is discharged out of the container from inside
the container; and a magnetic member that generates a magnetic
field that acts on the developer in the discharge path and causes
the developer to stay in the discharge path.
Inventors: |
OKUMA; Hiroaki; (Kanagawa,
JP) ; SUZUKI; Toshiaki; (Kanagawa, JP) ;
ISHII; Yasutomo; (Kanagawa, JP) ; HORII;
Kiyohito; (Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJI XEROX CO., LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
FUJI XEROX CO., LTD.
Tokyo
JP
|
Family ID: |
52132906 |
Appl. No.: |
14/200883 |
Filed: |
March 7, 2014 |
Current U.S.
Class: |
399/104 |
Current CPC
Class: |
G03G 15/0942 20130101;
G03G 15/0928 20130101 |
Class at
Publication: |
399/104 |
International
Class: |
G03G 15/08 20060101
G03G015/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 8, 2013 |
JP |
2013-142787 |
Claims
1. A developing device comprising: a developer carrier that has a
cylindrical shape and that rotates while holding developer to
supply the developer to an image carrier on which an electrostatic
latent image is formed; a container that contains the developer
carrier; a discharge-path forming member that forms a discharge
path along which air is discharged out of the container from inside
the container; and a magnetic member that generates a magnetic
field that acts on the developer in the discharge path and causes
the developer to stay in the discharge path.
2. The developing device according to claim 1, wherein the
discharge path is formed along an outer peripheral surface of the
developer carrier, and wherein the magnetic member is disposed in
the developer carrier.
3. The developing device according to claim 1, wherein the
discharge-path forming member forms the discharge path together
with an inner wall surface of the container, and wherein the
magnetic field generated by the magnetic member is capable of
retaining the developer that is in contact with the inner wall
surface in the discharge path.
4. The developing device according to claim 1, wherein the
discharge-path forming member covers a top portion of a path along
which an outer peripheral surface of the developer carrier moves,
the top portion being located at an uppermost position of the path,
and an outlet of the discharge path is located closer to the image
carrier than the top portion.
5. The developing device according to claim 1, wherein the
discharge path extends toward the image carrier.
6. The developing device according to claim 1, wherein the
discharge path covers a quarter or more of an outer peripheral
surface of the developer carrier.
7. The developing device according to claim 1, wherein an inlet
through which the air enters the discharge path is located below a
rotational axis of the developer carrier.
8. The developing device according to claim 1, wherein a cross
section of an outlet through which the air is discharged from the
discharge path is larger than a cross section of an inlet through
which the air enters the discharge path.
9. The developing device according to claim 3, wherein the
developer carried by the developer carrier does not contact a
surface of the discharge-path forming member, the surface facing
the developer carrier.
10. An image forming apparatus comprising: the developing device
according to claim 1; the image carrier that carries the
electrostatic latent image and receives the developer from the
developing device; and a transfer unit that transfers an image from
the image carrier onto a medium, the image being developed by the
developer supplied from the developing device.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and claims priority under 35
USC 119 from Japanese Patent Application No. 2013-142787 filed Jul.
8, 2013.
BACKGROUND
Technical Field
[0002] The present invention relates to a developing device and an
image forming apparatus.
SUMMARY
[0003] According to an aspect of the invention, a developing device
includes a developer carrier that has a cylindrical shape and that
rotates while holding developer to supply the developer to an image
carrier on which an electrostatic latent image is formed; a
container that contains the developer carrier; a discharge-path
forming member that forms a discharge path along which air is
discharged out of the container from inside the container; and a
magnetic member that generates a magnetic field that acts on the
developer in the discharge path and causes the developer to stay in
the discharge path.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] An exemplary embodiment of the present invention will be
described in detail based on the following figures, wherein:
[0005] FIG. 1 illustrates the overall structure of an image forming
apparatus according to an exemplary embodiment of the present
invention;
[0006] FIG. 2 illustrates the structure of a developing device;
[0007] FIG. 3 is an enlarged view of part II in FIG. 2;
[0008] FIG. 4 illustrates the shape of a discharge path according
to a modification; and
[0009] FIGS. 5A and 5B illustrate the arrangements of magnetic
members according to another modification.
DETAILED DESCRIPTION
1. Exemplary Embodiment
1-1. Overall Structure of Image Forming Apparatus
[0010] FIG. 1 illustrates the overall structure of an image forming
apparatus 1 according to an exemplary embodiment of the present
invention. In the following description, to describe the
arrangement of components of the image forming apparatus 1, the
space in which the components are arranged is represented by an xyz
right-handed coordinate system. Of the symbols of the coordinate
system illustrated in each figure, the white circle with a black
dot therein represents an arrow in the direction from the far side
to the near side in the figure. In the space, the direction along
the x-axis is referred to as an x-axis direction. In the x-axis
direction, the direction in which the x component increases is
referred to as a +x direction, and the direction in which the x
component decreases is referred to as a -x direction. Similarly, a
y-axis direction, a +y direction, a -y direction, a z-axis
direction, a +z direction, and a -z direction are defined for the y
and z components.
[0011] As illustrated in FIG. 1, the image forming apparatus 1
includes a controller 11, developing units 13Y, 13M, 13C, and 13K,
a transfer unit 14, a fixing unit 15, and a transport unit 16. The
letters Y, M, C, and K appended to the reference numeral 13
respectively represent yellow, magenta, cyan, and black toners. The
developing units 13Y, 13M, 13C, and 13K basically have similar
structures except for the color of the toner contained therein.
When it is not necessary to distinguish the developing units 13Y,
13M, 13C, and 13K from each other, the developing units will be
referred to simply as "developing units 13" without the letters
representing the toner colors appended at the end.
[0012] The controller 11 includes a storage unit such as a central
processing unit (CPU), a read only memory (ROM), a random access
memory (PAM), a solid state drive, or a hard disc drive. The CPU
reads computer programs stored in the storage unit and executes the
programs to control each part of the image forming apparatus 1.
[0013] The transport unit 16 includes a container and transport
rollers. The container contains sheets of paper P that are cut into
a predetermined size in advance and that serve as media. The sheets
of paper P contained in the container are fed one at a time by the
transport rollers and transported to the transfer unit 14 along a
sheet transport path in accordance with an instruction of the
controller 11. The media are not limited to sheets of paper, and
may instead be, for example, resin sheets. The media are not
particularly limited as long as images may be recorded on the
surfaces thereof.
[0014] Each developing unit 13 includes an image carrier 31, a
charging device 32, an exposure device 33, a developing device 34,
a first transfer roller 35, and a drum cleaner 36. The image
carrier 31 is a photoconductor drum that includes a charge
generating layer and a charge transport layer, and is rotated in
the direction of arrow D13 in FIG. 1 by a drive unit (not shown).
The charging device 32 charges the surface of the image carrier 31.
The exposure device 33 includes a laser source and a polygonal
mirror (neither is shown). The exposure device 33 is controlled by
the controller 11 so as to emit a laser beam corresponding to image
data toward the image carrier 31 that has been charged by the
charging device 32. Thus, an electrostatic latent image is formed
on the image carrier 31. The controller 11 may receive the
above-described image data from an external device through a
communication unit (not shown). The external device may be, for
example, a reading device capable of reading an original image or a
storage device that stores data representing an image. The
developing device 34 supplies developer to the image carrier 31.
Thus, an image is formed (developed) on the image carrier 31.
[0015] The first transfer roller 35 generates a predetermined
potential difference between the image carrier 31 and an
intermediate transfer belt 41 included in the transfer unit 14 at a
position where the image carrier 31 faces the intermediate transfer
belt 41. Owing to the potential difference, the image is
transferred onto the intermediate transfer belt 41. The drum
cleaner 36 removes the toner that has not been transferred and that
remains on the surface of the image carrier 31 after the
transferring of the image, and also removes the electricity from
the surface of the image carrier 31.
[0016] The transfer unit 14 includes the intermediate transfer belt
41, a second transfer roller 42, belt transfer rollers 43, a
back-up roller 44, and a belt cleaner 49. The transfer unit 14
transfers the images formed by the developing units 13 onto a sheet
of paper P. The intermediate transfer belt 41 is an endless belt
member and is wrapped around the belt transfer rollers 43 and the
back-up roller 44. At least one of the belt transfer rollers 43 and
the back-up roller 44 is provided with a drive unit (not shown)
that rotates the intermediate transfer belt 41 in the direction of
arrow D14 in FIG. 1. One or more of the belt transfer rollers 43
and the back-up roller 44 that have no drive unit are rotated by
the rotation of the intermediate transfer belt 41. When the
intermediate transfer belt 41 is rotated in the direction of arrow
D14 in FIG. 1, the images on the intermediate transfer belt 41 are
moved to the region between the second transfer roller 42 and the
back-up roller 44.
[0017] Owing to a potential difference between the second transfer
roller 42 and the intermediate transfer belt 41, the images on the
intermediate transfer belt 41 are transferred onto the sheet of
paper P that has been transported by the transport unit 16. The
belt cleaner 49 removes toner that has not been transferred and
that remains on the surface of the intermediate transfer belt 41.
The transfer unit 14 or the transport unit 16 transports the sheet
of paper P onto which the images have been transferred to the
fixing unit 15. The fixing unit 15 fixes the images that have been
transferred onto the sheet of paper P by applying heat thereto.
1-2. Structure of Developing Device
[0018] FIG. 2 illustrates the structure of the developing device
34. FIG. 3 is an enlarged view of part III shown in FIG. 2. As
illustrated in FIG. 2, the developing device 34 is below and at the
+y-direction side of the outer peripheral surface of the image
carrier 31, and includes a developer carrier 340, a magnet roller
344, and two screws 349. As illustrated in FIG. 3, the developing
device 34 further includes a container 341 and a discharge-path
forming member 342.
[0019] The container 341 contains two-component developer
containing Y, M, C, or K toner and magnetic carrier such as ferrite
powder. The container 341 also contains the developer carrier 340,
the magnet roller 344, and the two screws 349. The container 341
has an opening 3410 that faces the image carrier 31.
[0020] The magnet roller 344 is a columnar member which serves as a
magnetic-field generator that generates a predetermined magnetic
field around a side surface thereof with magnetic members, such as
permanent magnets, fixed therein. The magnetic field generated by
the magnetic members fixed in the magnet roller 344 acts on the
developer so that the developer is prevented from being discharged
out of the container 341. The developer carrier 340 is a so-called
developing sleeve which rotates around the magnet roller 344 while
holding the developer on the outer peripheral surface thereof,
thereby supplying the developer to the image carrier 31 having an
electrostatic latent image formed thereon. The developer carrier
340 is arranged so as to face the image carrier 31 in the opening
3410 of the container 341. The magnet roller 344 is fixed in the
developer carrier 340, and forms plural magnetic poles that extend
along an axial direction at predetermined angular positions. When
the developer carrier 340 passes the location of each magnetic pole
of the magnet roller 344, the developer on the developer carrier
340 receives a magnetic force.
[0021] As illustrated in FIG. 3, the magnetic poles of the magnet
roller 344 include a first pole S.sub.1, a transport pole N.sub.1,
and a separation pole S.sub.2. The first pole S.sub.1 is an S pole
for forming a magnetic brush that projects toward the image carrier
31 to supply the developer to the image carrier 31. The transport
pole N.sub.1 is an N pole for transporting the magnetic brush into
the container 341 after the supply of the developer is performed.
The separation pole S.sub.2 is an S pole for separating the
magnetic brush that has been transported into the container 341
from the surface of the developer carrier 340 and returning the
magnetic brush to a stirring region in which the screws 349 perform
stirring.
[0022] The developer carrier 340 is a nonmagnetic cylindrical
member that covers the outer peripheral surface of the magnet
roller 344. The developer carrier 340 rotates when a voltage is
applied thereto. When the developer carrier 340 is rotated by a
drive unit (not shown) in the direction of arrow D0 shown in FIG.
2, the developer, which receives a magnetic force from the magnet
roller 344, is transported in the direction of arrow D0.
[0023] The two screws 349 supply the developer to the developer
carrier 340 while stirring the developer. Owing to the magnetic
force applied by the magnet roller 344, the developer supplied to
the developer carrier 340 forms a magnetic brush having bristles
that extend along magnetic lines of force. The thus-formed magnetic
brush is retained by the developer carrier 340, and is moved by the
rotation of the developer carrier 340 to a position where the
magnetic brush faces the image carrier 31. When the tips of the
bristles come into contact with the surface of the image carrier
31, the toner adheres to portions of the surface of the image
carrier 31 that have been exposed to light by the exposure device
33, that is, to image portions of the electrostatic latent image.
Thus, an image is formed on the image carrier 31.
[0024] The discharge-path forming member 342 extends in the
rotational axis direction of the developer carrier 340 along the
outer peripheral surface of the developer carrier 340. The
discharge-path forming member 342 covers a portion of the developer
carrier 340 and forms a discharge path 343, through which the air
is discharged out of the container 341, between itself and the
inner wall of the container 341. The discharge-path forming member
342 is supported in the container 341 by ribs (not shown) provided
on portions of the inner wall surface of the container 341. The
discharge-path forming member 342 covers a top portion T of a path
along which the outer peripheral surface of the developer carrier
340 moves, the top portion T being located at the uppermost
position of the path. An outlet 3432 of the discharge path 343 is
closer to the image carrier 31 than the top portion T.
[0025] A valve V1 and a valve V2 are provided at the bottom side of
the opening in the container 341. The valve V1 is in contact with
the developer carrier 340 at an angle such that the distance
between the valve V1 and the surface of the developer carrier 340
decreases as the developer carrier 340 rotates further in the
direction of arrow D0. The valve V1 regulates the flow of air so
that the developer is not easily blown toward the image carrier 31
through a gap between the developer carrier 340 and the bottom side
of the opening. The valve V2 is in contact with the image carrier
31 so that the developer is prevented from being diffused.
[0026] A layer regulating member B, which is a member called, for
example, a trimmer bar, comes into contact with the magnetic brush
formed on the surface of the developer carrier 340 that rotates in
the direction of arrow D0, and scrapes off part of the magnetic
brush so that the height of the magnetic brush is adjusted to a
predetermined height. The developer that has been scraped off
returns to the screws 349. After the height of the magnetic brush
is adjusted, the magnetic brush passes through the position where
it faces the image carrier 31, supplies the toner to the surface of
the image carrier 31, and moves to a region R covered by the
discharge-path forming member 342.
[0027] The discharge-path forming member 342 is provided with a
valve V3. The valve V3 is in contact with the developer carrier 340
at an angle such that the distance between the valve V3 and the
surface of the developer carrier 340 decreases as the developer
carrier 340 rotates further in the direction of arrow D0. The valve
V3 regulates the flow of air so that the developer is not easily
blown toward the image carrier 31 through a gap between the
developer carrier 340 and the top side of the opening.
[0028] Thus, owing to the valve V and the valve V3, the air in the
container 341 does not easily flow toward the image carrier 31
through the opening 3410. Since the magnetic brush that passes the
valve V3 and reaches the top portion T moves into the container 341
together with the air, the inner pressure of the container 341
increases.
[0029] As illustrated in FIG. 3, for example, the discharge-path
forming member 342 covers the region R that extends over a quarter
or more of the entire outer peripheral surface of the developer
carrier 340 and that includes a portion located at the top portion
T. The magnetic brush having a height adjusted by the layer
regulating member B is formed on the developer carrier 340 when the
developer holder 340 reaches the region R. The discharge-path
forming member 342 is spaced from the developer carrier 340 so that
the discharge-path forming member 342 does not come into contact
with the magnetic brush. In this case, compared to the case in
which the discharge-path forming member 342 comes into contact with
the magnetic brush and breaks the magnetic brush, an amount of
developer that floats in the container 341 may be reduced.
[0030] The air in the container 341 flows in the direction of arrow
D1 shown in FIG. 3 and enters the discharge path 343 through an
inlet 3431. Since the discharge path 343 extends toward the image
carrier 31, the air that has entered through the inlet 3431 is
discharged through the outlet 3432 toward the image carrier 31 in
the direction of arrow D2. Thus, the increase in the inner pressure
of the container 341 is suppressed.
[0031] The relationship between the magnetic poles generated by the
magnet roller 344 and the discharge path 343 will now be described.
When, for example, the developing device 34 is detached from the
image forming apparatus 1 and tilted, there is a possibility that
the developer contained in the container 341 will enter the
discharge path 343 through the inlet 3431. As illustrated in FIG.
3, the discharge path 343 is located so as to cross the magnetic
lines of force that extend from the transport pole N.sub.1 and the
separation pole S.sub.2 generated by the magnet roller 344, and so
that the discharge path 343 is within a range in which the magnetic
fields generated by the transport pole N.sub.1 and the separation
pole S.sub.2 exert an attractive force. Therefore, even when the
developer enters the discharge path 343, the magnetic carrier
contained in the developer is affected by the magnetic lines of
force that extend from the transport pole N.sub.1 and the
separation pole S.sub.2 at the positions where the magnetic lines
of force cross the discharge path 343. In other words, the magnetic
members disposed in the magnet roller 344 generate the magnetic
fields that act on the developer in the discharge path 343, so that
the developer is kept in the discharge path 343. Thus, the magnetic
carrier is confined in the discharge path 343.
[0032] In the present exemplary embodiment, the magnetic fields
that attract the developer toward the magnet roller 344 extend to
the inner wall surface of the container 341. In other words, the
magnetic members provided in the magnet roller 344 generate the
magnetic fields in the discharge path 343, the magnetic fields
being capable of retaining the developer that is in contact with
the inner wall surface of the container 341. Therefore, even when a
large amount of developer enters the discharge path 343, magnetic
brushes are formed which extend to a height such that the magnetic
brushes contact the inner wall surface of the container 341 at
positions corresponding to the transport pole N.sub.1 and the
separation pole S.sub.2 in the discharge path 343. As a result, the
possibility that the developer that has entered the discharge path
343 will be discharged out of the developing device 34 through the
outlet 3432 is reduced.
[0033] As described above, in the developing device 34, the
discharge path 343 is arranged so as to cross the magnetic lines of
force that extend from the separation pole S.sub.2 and the like
generated by the magnet roller 344. Thus, the possibility that the
developer will be discharged to the outside through the discharge
path 343 for discharging the air out of the container 341 is
reduced.
[0034] Referring to FIG. 3, the discharge path 343 may be formed
such that the gap W.sub.2 of the outlet 3432 is greater than the
gap W.sub.1 of the inlet 3431. Here, the "gap" of the discharge
path 343 is the dimension of the discharge path 343 along the
radial lines extending from the rotational axis O of the developer
carrier 340 toward the outer peripheral surface of the developer
carrier 340. In the case where the lengths of the outlet 3432 and
the inlet 3431 are both the same as of that of the developer
carrier 340 in the axial direction, the outlet 3432, which has a
larger gap, has a larger cross section than the inlet 3431. Namely,
the cross section of the outlet 3432 through which the air is
discharged from the discharge path 343 is larger than the cross
section of the inlet 3431 through which the air enters the
discharge path 343. As a result, the velocity at which the air
passes through the outlet 3432 is lower than the velocity at which
the air passes through the inlet 3431, and the possibility that the
developer will be discharged from the discharge path 343 by the air
may be further reduced.
[0035] Since the air containing the developer tends to stay around
the image carrier 31, a cloud processing device that sucks the air
that stays around the image carrier 31 is commonly arranged near
the image carrier 31. As described above, the discharge path 343
extends toward the image carrier 31. Therefore, in the case where
the cloud processing device is provided, the air in the container
341 of the developing device 34 may be processed by the cloud
processing device even when no additional processing device is
provided.
[0036] The discharge path 343 extends along the outer peripheral
surface of the developer carrier 340, and covers the top portion T
of the path along which the outer peripheral surface moves, the top
portion T being located at the uppermost position of the path.
Therefore, the air that flows into the discharge path 343 through
the inlet 3431 flows against the gravity until the air passes the
top portion T. Accordingly, the developer contained in the air may
be easily removed due to gravity before the air passes the top
portion T, and the possibility that the toner contained in the
discharged air will stain the medium or the like may be
reduced.
2. Modifications
[0037] Although an exemplary embodiment has been described above,
the exemplary embodiment may be modified as follows.
[0038] The modifications described below may be employed in
combination.
2-1. First Modification
[0039] In the above-described exemplary embodiment, the discharge
path 343 extends toward the image carrier 31. However, it is not
necessary that the discharge path 343 extend toward the image
carrier 31 as long as the discharge path 343 is closer to the image
carrier 31 than the top portion T.
[0040] FIG. 4 illustrates the shape of a discharge path 343a
according to this modification. In this modification, a developing
device 34a includes a developer carrier 340a, a magnet roller 344a,
a container 341a, and a discharge-path forming member 342a. The
developing device 34a differs from the above-described developing
device 34 in that an image-carrier-31-side end portion (the image
carrier 31 is not illustrated in FIG. 4) of a part of the container
341a that covers the developer carrier 340a from above is farther
from the image carrier 31 than an image-carrier-31-side end portion
of the discharge-path forming member 342a. Therefore, an outlet
3432a of the discharge path 343a does not face the image carrier
31. However, as illustrated in FIG. 4, the above-described
image-carrier-31-side end portions of the container 341a and the
discharge-path forming member 342a are both closer to the image
carrier 31 than the top portion T. As a result, also in this
modification, the outlet 3432a is closer to the image carrier 31
than the top portion T. Therefore, in the case where the
above-described cloud processing device is arranged near the image
carrier 31, the air in the container 341a of the developing device
34a may be processed by the cloud processing device even when no
additional processing device is provided.
2-2. Second Modification
[0041] In the above-described exemplary embodiment, the
discharge-path forming member 342 covers a region that extends over
a quarter or more of the entire outer peripheral surface of the
developer carrier 340 and that includes a portion located at the
top portion T. However, it is not necessary that the region covered
by the discharge-path forming member 342 extend over a quarter or
more of the entire circumference of the developer carrier 340 as
long as, for example, the inlet 3431 through which the air enters
the discharge path 343 is below the rotational axis O of the
developer carrier 340.
2-3. Third Modification
[0042] In the above-described exemplary embodiment, the
discharge-path forming member 342 forms the discharge path 343 such
that the discharge path 343 extends along the outer peripheral
surface of the developer carrier 340 and covers a portion of the
developer carrier 340. However, it is not necessary that the
discharge path 343 extend along the outer peripheral surface of the
developer carrier 340.
[0043] In addition, although the magnetic members, such as
permanent magnets, that prevent the developer from being discharged
out of the container 341 are disposed in the magnet roller 344, the
magnetic members may instead be disposed outside the magnet roller
344. The magnetic members are not limited to permanent magnets. The
magnetic members may instead be electromagnets as long as the
developer may be prevented from being discharged out of the
container 341.
[0044] FIGS. 5A and 5B illustrate the arrangements of magnetic
members in such a modification. FIG. 5A illustrates a
discharge-path forming member 342b that forms a discharge path 343b
and a magnetic member M.sub.1 provided along the discharge path
343b. Hereinafter, components of a developing device 34b according
to this modification are denoted by reference symbols obtained by
adding the letter `b` to the reference symbols of the corresponding
components of the developing device 34 according to the
above-described exemplary embodiment.
[0045] The discharge-path forming member 342b illustrated in FIG.
5A is provided at an opening formed in a housing of a container
341b, the opening being further toward the +y-direction side than a
developer carrier 340b. The discharge-path forming member 342b
extends in the +y direction from the edge of the opening. The
discharge path 343b, which is formed by the discharge-path forming
member 342b, also extends in the +y direction. In this case, it is
not necessary that the discharge path 343b be formed between the
discharge-path forming member 342b and the inner wall surface of
the container 341b. As illustrated in FIG. 5A, the magnetic member
M.sub.1 is provided along the discharge path 343b, and generates a
magnetic pole S.sub.3 toward the discharge path 343b. The magnetic
field generated by the magnetic pole S.sub.3 acts on the developer
in the discharge path 343b so that the developer is prevented from
being discharged out of the container 341b.
[0046] In the above-described exemplary embodiment, the
discharge-path forming member 342 covers the top portion T of the
path along which the outer peripheral surface of the developer
carrier 340 moves, the top portion T being located at the uppermost
position of the path, and the outlet 3432 of the discharge path 343
is located closer to the image carrier 31 than the top portion T.
However, the arrangement of the discharge path and the outlet is
not limited to this. FIG. 5B illustrates a developing device 34c in
which a discharge-path forming member 342c forms a discharge path
343c that extends along the outer wall of a housing of a container
341c. Hereinafter, components of the developing device 34c
according to this modification are denoted by reference symbols
obtained by adding the letter `c` to the reference symbols of the
corresponding components of the developing device 34 according to
the above-described exemplary embodiment.
[0047] The container 341c contains a developer carrier 340c and two
screws 349c. The two screw 349c are located further toward the
-z-direction side and +y-direction side than the developer carrier
340c, and the housing of the container 341c is shaped so as to
extend along the screws 349c. The housing of the container 341c has
an opening at the +y-direction side of the developer carrier 340,
and the discharge-path forming member 342c extends from the opening
along the outer wall of the housing of the container 341c. The
discharge-path forming member 342c and the outer wall surface of
the housing of the container 341c form the discharge path 343c. As
illustrated in FIG. 5B, a magnetic member M.sub.2 is provided along
the discharge path 343c, and the magnetic field generated by the
magnetic member Ms acts on the developer in the discharge path 343c
so that the developer is prevented from being discharged out of the
container 341c.
[0048] In this modification, the inner wall surface of the housing
of the container 341c may be formed so that the inner wall surface
does not come into contact with the magnetic brush held by the
developer carrier 340c. In this case, compared to the case in which
the inner wall surface of the housing of the container 341c comes
into contact with the magnetic brush and breaks the magnetic brush,
an amount of developer that floats in the container 341c may be
reduced.
[0049] The foregoing description of the exemplary embodiment of the
present invention has been provided for the purposes of
illustration and description. It is not intended to be exhaustive
or to limit the invention to the precise forms disclosed.
Obviously, many modifications and variations will be apparent to
practitioners skilled in the art. The embodiment was chosen and
described in order to best explain the principles of the invention
and its practical applications, thereby enabling others skilled in
the art to understand the invention for various embodiments and
with the various modifications as are suited to the particular use
contemplated. It is intended that the scope of the invention be
defined by the following claims and their equivalents.
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